Coral Reefs and Lagoons
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Transcript Coral Reefs and Lagoons
Part I
Section 5
Invertebrate marine animal
A polyp that begins to form an exoskeleton
◦ CO2 & Ca in the water to make calcium carbonate
(CaCO3) aka limestone
Sessile – immobile
Form colonies
Coral atolls
1st proposed by
Charles Darwin
◦ HMS Beagle (Nov
1835 – Apr 1836)
Supported and
modified by 2
geologists
◦ James Daly
◦ Reginald Dana
1. Oceanic volcano emerges from sea surface
and forms an island
◦ Colonized by reef-building corals
2. Growth of corals forms a fringing reef
around the island
◦ Fringing reef – coral structure attached to the
mainland or continental islands
Island begins to sink slowly
Coral growth continues
3. Island continues to sink
Barrier reef forms with lagoon around reef
and island
◦ Barrier reef - reef separated from a mainland or
island shore by a deep channel or lagoon
4. Island eventually disappears below sea
surface
Atoll - consists of a ring of small islands
Shallow lagoon in center
Fringing reef can take
10,000 years to form
Atolls up to 30 my
Coral – tan and purple
Data from deep drilling on coral atolls
◦ Bikini Atoll (Pacific Ocean)
◦ As depth of corals increased, age of corals also
increased
◦ Fossil corals dated 50 myo and found 1200 m deep
Grown on underlying volcanic rock
◦ Shallow corals found at deep depths!
Darwin (1842) produced 1st map of
distribution of corals
3 main types:
◦ Fringing barrier reefs, barrier reefs, atolls
Conditions required:
◦ Temperature range =16⁰C – 35 ⁰C
Optimum range = 23 ⁰C - 25 ⁰C
◦ Water clarity
Clear water (less turbid) without silt
Silt reduces light penetration which inhibits photosynthesis of
symbiotic zooxanthellae in coral tissues (90% nutrients provided)
Depth – rapid growth occurs within 20 m from surface
◦ Salinity
◦ Substrate – surface on which plant/animals live
Basaltic rocks of seamounts
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What’s going
on here?
Shoreline protection from erosion ◦ Dissipates/absorbs energy of waves
Benefits include protection of
◦ Coastal properties
◦ Ecosystems
◦ Costs to provide breakwaters – constructed
structures for protection from erosion
◦ Anchorage of boats
Coral Gardens Fiji (Pacific Ocean)
Egypt (Red Sea)
Baja
Due Friday!
Read Marine Biology book pages 10-1
◦ Answer question 1 AND write bolded words with
definitions!
◦ Dropbox it in complete sentence(s)
Your NEW Oceanography textbooks are in!!!!!